Climate matching models for Ceratapion basicorne (Coleoptera: Apionidae), a biocontrol agent of yellow starthistle

Ceratapion basicorne (Illiger) (Coleoptera: Apionidae), a weevil native to Europe and western Asia, shows promise for enhancing the control of yellow starthistle (Centaurea solstitialis L.), an invasive annual forb in the western U.S. However, a paucity of data on this biocontrol agent’s environmental constraints has made it difficult to assess the suitability of potential release locations. Climate matching models were developed for C. basicorne to help identify areas of the western U.S. with similar climates to the source area of breeding colonies being used for releases (home location). The models used climate variables derived from daily estimates of minimum temperature, maximum temperature, precipitation, and soil moisture for a 30-year period spanning 1991−2020 at 1 km2 resolution. Of the areas where C. solstitialis is known to occur, the Central California Foothills, Eastern Cascades Foothills, Columbia Plateau, and mountainous parts of northcentral Utah had the most similar climates to the home location. Of these areas, the Eastern Cascades foothills in northeastern California and the Wasatch Range in Utah occurred at a similar latitude as the home location, which may be important to consider if C. basicorne has photoperiodic diapause. The least similar climates occurred in wet coastal regions, high-elevation (cold) mountains, and hot deserts; however, C. solstitialis has not been detected in most of these areas. The development of process-based models for predicting the establishment of this agent will require a more detailed understanding of the agent’s requirements for development and survival.

Methods
The details of the Methods are described in the publication and summarized below. The README file provides more details about the data and file structure.

Climate data: climate matching models for C. basicorne used averages of minimum and maximum temperatures (Tmax and Tmin, respectively), precipitation, and soil moisture for a 30-year period spanning 1991−2020. Daily temperature and precipitation data were derived from the Daymet dataset for North America at 1 km2 resolution (https://daymet.ornl.gov/getdata, accessed 17 May 2024) and the E-OBS dataset for Europe at 0.1° deg resolution (ca. 11.1 km2; https://surfobs.climate.copernicus.eu, accessed 13 Jul 2022). Daily soil moisture estimates at the first 5 cm depth were derived from the Simple Terrestrial Hydrosphere model, version 2 (SiTHv2) at 0.1° deg resolution. SiTHv2 data were downscaled to 1-km2 resolution for the western U.S. to match the resolution of Daymet data. All datasets were temporally aggregated to a weekly and monthly resolution for modeling. See the README file for more details.

County-level detections for yellow starhistle: these were estimated from GBIF and EDDMaPS data.